What are the causes of bradycardia and anorexia?

Causes of Bradycardia and Anorexia

Anorexia nervosa is a significant cause of bradycardia, with up to 95% of anorexia patients experiencing heart rates below 60 beats per minute, often due to increased parasympathetic tone and metabolic adaptations to starvation. 1

Common Etiologies of Bradycardia and Anorexia Together

Primary Eating Disorders

• Anorexia Nervosa
  • Severe weight loss enhances parasympathetic nervous system activity 2
  • Metabolic adaptations to conserve energy during starvation
  • Heart rates may drop as low as 26-32 bpm in severe cases 2, 1
  • Typically reversible with nutritional rehabilitation

Endocrine Disorders

• Hypothyroidism
  • Can cause both bradycardia and decreased appetite
  • May present with "mosque sign" - dome-shaped symmetric T waves without ST segment 3
  • Often accompanied by fatigue, cold intolerance, and weight changes
  • Functional hypothyroidism can develop secondary to anorexia nervosa 2

Medications and Toxins

• Cardiac Medications

  • Beta-blockers (sotalol, etc.) 3
  • Calcium channel blockers
  • Antiarrhythmics (amiodarone, lidocaine) 3
  • These medications can cause bradycardia and may have gastrointestinal side effects affecting appetite

• Other Medications

  • Opioids
  • Certain psychiatric medications
  • Digoxin toxicity

Neurological Conditions

• Central Nervous System Disorders 3
  • Increased intracranial pressure
  • Meningitis
  • Brain tumors affecting hypothalamus (appetite center)
  • These can affect both cardiac regulation and appetite control centers

Systemic Illnesses

• Infectious Diseases

  • Typhoid fever 3
  • Viral myocarditis
  • HIV infection
  • Systemic infections causing both bradycardia and anorexia

• Connective Tissue Disorders

  • Lupus erythematosus with anti-Ro/SSA antibodies 3
  • Can affect both cardiac conduction and cause systemic symptoms including anorexia

Diagnostic Approach

1. Vital Signs Assessment

   • Heart rate <50 bpm typically indicates clinically significant bradycardia 3
   • Check for hypotension, which often accompanies bradycardia in anorexia

2. Physical Examination

   • Calculate BMI (BMI <18.5 suggests malnutrition)
   • Assess for cachexia, muscle wasting, skin changes
   • Evaluate for signs of hypothyroidism (dry skin, hair loss, delayed reflexes)

3. Laboratory Testing

   • Electrolytes (hypokalemia, hypomagnesemia can worsen bradycardia)
   • Thyroid function tests (TSH, free T3, free T4)
   • Complete blood count
   • Liver function tests

4. Cardiac Evaluation

   • 12-lead ECG to characterize bradycardia (sinus vs. AV block) 3
   • Echocardiogram if structural heart disease suspected
   • Consider Holter monitoring for intermittent bradycardia

Management Considerations

Acute Management

• For symptomatic bradycardia with hemodynamic compromise:
  • Atropine may be reasonable to increase heart rate 3
  • Use with caution as it may mask underlying causes
  • Beta agonists (isoproterenol, dopamine) may be considered in patients with low risk of coronary ischemia 3

Addressing Underlying Causes

• For Anorexia Nervosa

  • Nutritional rehabilitation is the definitive treatment 2, 4
  • Bradycardia typically resolves with weight restoration
  • Multidisciplinary approach with psychiatric support

• For Hypothyroidism

  • Thyroid hormone replacement therapy
  • Monitor cardiac response to treatment

• For Medication-Induced Bradycardia

  • Consider medication adjustments or discontinuation when possible 3
  • Temporary pacing may be needed in severe cases

Special Considerations

• Refeeding Syndrome

  • Potentially life-threatening complication during nutritional rehabilitation of severely malnourished patients 3
  • Can worsen cardiac abnormalities
  • Requires careful electrolyte monitoring and gradual refeeding

• Age-Specific Considerations

  • Pediatric patients have higher normal heart rates; bradycardia thresholds differ 3
  • Elderly patients have increased sensitivity to medications that cause bradycardia 5

• Monitoring During Recovery

  • Serial ECGs to track improvement in heart rate
  • Regular weight monitoring
  • Electrolyte monitoring, especially during refeeding

The combination of bradycardia and anorexia should always prompt evaluation for eating disorders, particularly in young females, but other medical causes must be ruled out before attributing symptoms solely to psychiatric conditions.